CVE-2026-9460: Edimax EW-7438RPn Buffer Overflow Flaw

CVE-2026-9460 Overview

CVE-2026-9460 is a stack-based buffer overflow vulnerability affecting Edimax EW-7438RPn firmware version 1.31. The flaw resides in the formAccept function within /goform/formAccept, where the submit-url argument is processed without proper bounds checking. Attackers can exploit the weakness remotely over the network to corrupt stack memory on the embedded device.

The exploit code has been publicly disclosed, and the vendor did not respond to disclosure attempts. The vulnerability is classified under [CWE-119] (Improper Restriction of Operations within the Bounds of a Memory Buffer).

Critical Impact
Remote attackers with low privileges can trigger a stack-based buffer overflow in the router's web management interface, potentially leading to arbitrary code execution or device compromise.

Affected Products

Edimax EW-7438RPn firmware version 1.31
The vulnerable component is the formAccept handler at /goform/formAccept
The affected parameter is the submit-url HTTP argument

Discovery Timeline

2026-05-25 - CVE-2026-9460 published to NVD
2026-05-26 - Last updated in NVD database

Technical Details for CVE-2026-9460

Vulnerability Analysis

The vulnerability resides in the formAccept function exposed through the device's web management interface at /goform/formAccept. The handler accepts the submit-url parameter from HTTP requests and copies it into a fixed-size stack buffer without validating the input length. When the supplied value exceeds the buffer size, adjacent stack memory is overwritten, including saved return addresses.

An attacker reachable over the network can submit a crafted HTTP request containing an oversized submit-url value. Successful exploitation may corrupt control flow and lead to arbitrary code execution within the context of the web server process, which typically runs with elevated privileges on embedded devices. Public exploit material is available, and the vendor has not issued a patch or acknowledgement.

Root Cause

The root cause is the absence of length validation before copying user-supplied data into a stack-resident buffer. Embedded HTTP handlers in this firmware use unsafe string operations against attacker-controlled inputs, allowing the submit-url parameter to overflow its allocated space. This pattern matches [CWE-119], where memory operations are performed outside the intended boundaries.

Attack Vector

Exploitation occurs through the network attack surface. The attacker requires low-level authentication context to reach the /goform/formAccept endpoint but does not need user interaction. A single HTTP POST request with a malformed submit-url argument triggers the overflow. On routers exposed to untrusted networks or with weak default credentials, the impact extends to full device takeover.

The vulnerability mechanism involves sending an HTTP request to the embedded web server with the submit-url POST field set to a value substantially larger than the destination buffer. Refer to the GitHub Vulnerability Documentation and VulDB #365441 for proof-of-concept details.

Detection Methods for CVE-2026-9460

Indicators of Compromise

HTTP POST requests targeting /goform/formAccept with abnormally long submit-url parameter values
Unexpected reboots or crashes of the Edimax EW-7438RPn web management daemon
Outbound connections from the router to unknown hosts following administrative access events
Modified configuration entries or unauthorized firmware changes on the device

Detection Strategies

Inspect HTTP traffic destined for router management interfaces for parameter lengths exceeding expected sizes
Deploy network intrusion detection signatures that match oversized submit-url values in requests to /goform/formAccept
Correlate router crash events with preceding HTTP activity from internal or external sources
Baseline normal administrative request patterns and alert on deviations targeting the formAccept handler

Monitoring Recommendations

Log all HTTP requests to embedded device management endpoints and forward them to a centralized analytics platform
Monitor for repeated POST requests to /goform/formAccept from a single source within short time windows
Track firmware integrity and configuration drift on Edimax EW-7438RPn devices
Alert on any administrative access to the router from non-management network segments

How to Mitigate CVE-2026-9460

Immediate Actions Required

Restrict access to the router's web management interface to trusted administrative networks only
Disable remote management features on the Edimax EW-7438RPn if not strictly required
Change default credentials and enforce strong authentication on the device
Place affected devices behind a network segmentation boundary or firewall ACL that blocks untrusted access to /goform/formAccept

Patch Information

No vendor patch is available. According to the disclosure, the vendor was contacted but did not respond. Organizations operating the Edimax EW-7438RPn 1.31 should treat the device as unpatched and consider replacement with a supported model if continued exposure is unacceptable. Monitor the VulDB advisory for any future vendor updates.

Workarounds

Isolate the device on a dedicated VLAN with strict ingress and egress filtering
Block external access to TCP ports used by the web management interface at the perimeter firewall
Replace the affected hardware with a vendor-supported device that receives security updates
Apply web application firewall rules upstream to drop HTTP requests containing oversized submit-url parameters bound for the device

bash

# Example iptables rule to restrict management interface access to a trusted subnet
iptables -A FORWARD -p tcp -d <router_ip> --dport 80 -s 10.0.0.0/24 -j ACCEPT
iptables -A FORWARD -p tcp -d <router_ip> --dport 80 -j DROP